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Documentation Index

Fetch the complete documentation index at: https://docs.zayo.com/llms.txt

Use this file to discover all available pages before exploring further.

Before tackling complex scenarios, it is essential to master the foundational tools for active troubleshooting. The Looking Glass utility and the ARP table provide definitive, real-time answers to fundamental questions about connectivity and reachability.

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Looking Glass

The Looking Glass tool is a suite of active diagnostic utilities that allow you to test the network path from the perspective of the platform itself.
ToolFunctionPrimary Use Case
Route LookupVerifies route visibility from a location.”Is my new VPC route correctly advertised to my branch office?”
PingTests end-to-end reachability and latency.”Can my server reach the public internet?”
TracerouteTraces the hop-by-hop path to a destination.”Where is the latency or packet loss occurring on the path to my application?”
Path MTU DiscoveryDetermines the maximum packet size on a path.”Is a mismatched MTU causing performance degradation?”
Packet CaptureCaptures raw network traffic for deep analysis.”I need to analyze the full packet flow to debug a complex protocol issue.”

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ARP Table

The Address Resolution Protocol (ARP) Table is another fundamental tool, used to validate Layer 2 connectivity and provide crucial clues for Layer 3 troubleshooting. By navigating to Network -> Cloud Router -> ARPs, you can see the mapping of IP addresses to MAC addresses on a given interface.

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Use Case: Troubleshooting BGP

The presence of an ARP entry for a BGP peer’s IP address is a definitive confirmation that Layer 2 connectivity (e.g., the correct VLAN, physical link) is established. If BGP peering is failing, but a valid ARP entry exists for the peer, the problem is almost certainly a Layer 3 BGP configuration error (such as an incorrect AS number or a mismatched authentication key) and not a physical or VLAN issue. This allows you to immediately focus your efforts on the correct configuration domain.